Radioactive Detectors
Cloud Chamber
A cloud chamber is used to show the path of ionizing radiation. The tracks of the radioactive emission are formed in the same way as the condensation trails behind a high-flying aero plane when the air in the sky is cold and damp enough. Different tracks are formed for each radioactive emission.
Tracks of radioactive emissions
Geiger-Muller Tube
A Geiger-Muller tube (GM tube) is a very versatile, sensitive and useful detector of radiation. It operates at a voltage of about 450 V. Radiation enters the GM tube through the mica window and ionizes the argon gas. A pulse of current is produced. This pulse of current is counted by a scalar or a rate meter. The scalar gives the number of counts over a certain period of time. The rate meter gives the count rate in counts per second or counts per minute. The GM tube can detect alpha particles, beta particles and gamma rays.
Photographic Film
A photographic film found in badges worn by the staff at radiation laboratories is developed at the end of every month. The degree of darkening of the photographic film indicates the amount of radiation received.
Spark Counter
A spark counter uses the ionizing effect of radiation. A high voltage is applied between the gauze and a wire below the gauze, and adjusted until it is just below the voltage required to produce sparks. When a radioactive source is brought near, the radiation ionizes the air between the gauze and the wire, and sparks are produced. Spark counters are suitable for detecting alpha particles.
Characteristics of radioactive emissions
There are three kinds of radioactive emissions
• Alpha particles
• Beta particles
• Gamma rays
Penetrating powers of radioactive emissions
Alpha decay
An alpha particle is emitted. The proton number is reduced by two and the nucleon number is reduced by four. These particles are positively charged.
Beta decay
A beta particle is emitted. The proton number is increased by one and the nucleon number is unchanged. These particles are negatively charged.
Gama decay
A gamma ray proton is emitted. The proton number and nucleon number are unchanged. This particle does not carry any charge.
The effect of an electric field on the radioactive emissions
The effect of a magnetic field on the radioactive emissions
Radioactivity-Nuclear
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